[time-nuts] RE : Re: FASTRAX GPS
jwsmail at jwsss.com
Wed Jul 2 17:49:17 EDT 2014
On 7/2/2014 1:29 PM, Jean-Louis Oneto wrote:
> AFAIK, the differential variant of RS-232 is RS-485. I'm not sure about the levels.
> Best regards,
> Jean-Louis Oneto
You have to control the direction of RS485. You don't have to with
RS232. One of the problems with support of RS485 in Linux OS kernels is
that the kernel can't respond to the turning of the line quickly enough
in real time. I had an application with 115k requirement, and it had to
turn the line within 1/10 of a bit time. Pretty quick for a kernel.
It is differential, and it does send data, but is a different beast in
I would have liked to have had an external processor to handle the
RS485, and some chips do that, but we had the engineer just attach two
serial ports on an Arm SOC to the usual serial uarts, and it was fun
figuring out how to make it work.
BTW this was for communicating with an airframe, and the avionics
dictated the rate we had to turn the lines. It was for passenger
signals, etc., so was simple, but you basically ran all the cabin
lighting and attendant signalling thru one line for the entire aircraft.
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